Capillary Flow Porometry

The pore size distributions and N₂ permeability of the electrospun membranes were measured by capillary flow porometry (Porolux 1000, POROMETER, Belgium). This employed the gas–liquid displacement method using perfluoropolyether (Porefil 125, surface tension = 15.88 ± 0.03 mN m^–1) as the wetting liquid as detailed in our previous work.⁶² The slope of the dry curve was used to calculate the nitrogen permeability by dividing by the membrane thickness. This technique was also used to measure the liquid entry pressure (LEP) of the membranes. Using a nonstandard method, 13 mm disks were cut from each membrane and inserted dry into the Porolux device. Then, 0.3 mL of DI water was dropped onto the surface of the membrane, and the compartment was closed by connecting the gas. The Porolux was set to provide a maximum pressure of 1 bar over 50 steps, and the “full porometry” program was executed. This gradually increased the pressure on the water sat atop the membrane. As the pressure continued to increase, a sudden increase in gas flow was measured by the device, indicating that the water was forced through the membrane. The pressure at which this occurred was reported as the LEP. For all measurements, the reported values are averages of three samples taken from different areas on the membrane.